Learn Italian: Ci sono voluti mesi, ma finalmente si sono permesse le esportazioni. - It took months, but finally the exports were permitted.

This sentence uses the si passivante (passive 'si'). The noun receiving the action, le esportazioni (the exports), becomes the grammatical subject. In compound tenses with the si passivante, you must always use the auxiliary verb essere. Because le esportazioni is feminine plural, the auxiliary becomes sono and the past participle takes the feminine plural ending -e, giving us sono permesse.

Why does the first part of the sentence use sono voluti?

This uses the verb volerci, which means 'to take' regarding time or effort. A tricky aspect of volerci is that the time or effort required is the actual grammatical subject. Here, the subject is mesi (months). Since mesi is masculine plural, the auxiliary verb must be plural (sono), and the past participle must agree with it, ending in -i to form voluti.

Could I put the subject before the verb and say le esportazioni si sono permesse?

Grammatically, yes. However, putting the subject after the verb is highly typical for the si passivante in Italian. This inverted word order sounds much more natural, particularly when you are reporting an event or announcing that a status has changed, such as exports finally being allowed.

How do we know isn't a reflexive verb here?